Commodore 1541 Floppy Drive Hardware Failure Cheat Sheet
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Commodore Diagnostician II
By Ian Perry, Kyneton, Victoria 3444, Australia   Sept 1989

Symptomatic Chart Diagnosing
Faulty IC Components On
Commodore 1541
Floppy Drive

6502 6522 325302 901229 LB311 592 9602 325572
Error LEB blinks on power up x x
Searching with no red LED x x
Drive fails to read x x x x
Fails to fomat x x
Stepper motor does not step x x
Will not save when drive heats up x x
Lights stay on, motor runs continuously x x
No LEDs on power up Check power supply voltage, Check CR3, VR2, VR1, CR1
Drive motor runs continuously with no green LED Check 5Volt on power supply
Flashing light on and off  Check UC1, UD2
Message of ‘FILE NOT FOUND’ is displayed Check alignment, defective disk
Drive speed will not stabilize Clean drive head w/ Alcohol, check alignment
Display reads ERROR 21-29 (Disk Errors) Checl PCB speed (LAG570 – for Newt. Drive)
Write protect on ERROR #25 Check WPS, UA1, Write Protect Switch, alignment
Track 18 Display 21 read ERROR Check alignment, UC2, UE6, check R/W head
Will not load certain programs Check alignment, track 0 stop